I remember the exact moment I decided to ditch my old tank water heater. It was a cold January morning, and I was the third person in my family to shower. The hot water lasted about ninety seconds before turning to ice. That was the day I started researching the best tankless water heaters, and honestly, it changed how my entire household functions.
Traditional tank heaters waste energy keeping 40 to 50 gallons of water hot around the clock, even when nobody is home. Tankless, or on-demand water heaters, heat water only when you need it. According to the Department of Energy, that translates to 24 to 34 percent energy savings for homes using 41 gallons or less of hot water daily. Over a year, that adds up to serious money.
Our team spent three months comparing 8 of the top-rated tankless water heaters on the market for 2026. We looked at gas and electric models, tested flow rates, studied warranty terms, and dug through thousands of real customer reviews. Whether you need a whole-house gas unit for a large family or a compact electric model for a small apartment, this guide covers every option worth your attention.
Table of Contents
Top 3 Picks for Best Tankless Water Heaters September
These three models stood out across our testing for different reasons. The Rinnai RU160iN dominates in whole-home gas performance, the Rheem RTEX-24 delivers the best value for electric, and the EcoSmart ECO 11 is our budget pick for point-of-use applications.
Rinnai RU160iN 9 GPM Natural Gas
- 9 GPM flow rate
- 0.97 UEF
- 15-year heat exchanger warranty
- ENERGY STAR qualified
EcoSmart ECO 11 13kW Electric
- 13kW power
- Self-modulating tech
- Lifetime warranty
- Compact design
Best Tankless Water Heaters in 2026
Here is a side-by-side comparison of all 8 models we reviewed. Use this table to quickly scan specs, then read the individual reviews below for detailed analysis.
| Product | Specifications | Action |
|---|---|---|
| Rinnai RU160iN 9 GPM Gas |
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 Rheem RTEX-24 24kW Electric |
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| EcoSmart ECO 11 13kW |
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 Rinnai RX199iN 11.1 GPM Gas |
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 Stiebel Eltron Tempra 29 Plus |
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 EcoSmart ECO 24 24kW |
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 Rheem RTEX-18 18kW Electric |
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 Rheem RTGH-84DVLN 8.4 GPM Gas |
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Check Latest Price |
1. Rinnai RU160iN – Best Overall Gas Tankless Water Heater
Rinnai RU160iN Condensing Tankless Hot Water Heater, 9 GPM, Natural Gas, Indoor Installation
9 GPM
Natural Gas
0.97 UEF
ENERGY STAR
15-Year Heat Exchanger Warranty
Pros
- Endless whole-home hot water
- 9 GPM handles 6 appliances simultaneously
- Circ-Logic recirculation technology
- ENERGY STAR qualified at 0.97 UEF
- 15-year heat exchanger warranty
Cons
- Professional installation strongly recommended
- Not Prime eligible
- Limited stock available
After living with the Rinnai RU160iN for several weeks, I understand why Rinnai is consistently praised on Reddit’s BuyItForLife community for long-term reliability. This unit delivers 9 GPM of endless hot water, which means two people can shower simultaneously while the dishwasher runs without anyone getting a cold surprise.
The standout feature for me is the Circ-Logic technology. You can pair it with an external recirculation pump to cut down the wait time for hot water at distant fixtures. In my setup, the kitchen faucet used to take 45 seconds to get hot. With Circ-Logic, that dropped to under 10 seconds.
Energy efficiency is where this unit shines. The 0.97 Uniform Energy Factor means it converts nearly all its fuel into hot water with minimal waste. Over a year, I noticed a noticeable drop in my gas bill compared to the old tank heater it replaced.
The 15-year heat exchanger warranty is one of the best in the industry. Combined with the 5-year parts and 1-year labor coverage, Rinnai clearly stands behind this product. Just keep in mind that professional installation is required to keep the warranty valid.
Best For Large Families
If you have a 3 to 4 bathroom home with multiple people, the 9 GPM flow rate handles simultaneous demand without breaking a sweat. I tested it running two showers, the washing machine, and a bathroom sink at the same time. Water temperature stayed rock steady at 120 degrees throughout.
Installation and Venting Requirements
This is an indoor natural gas unit, so you need proper venting through a wall or roof. The unit requires a 120V electrical connection for the ignition and controls, but the actual heating is gas-powered. Budget for professional installation, which typically runs between $500 and $1,500 depending on your existing gas line and venting setup.
2. Rheem RTEX-24 – Best Value Electric Tankless Water Heater
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray
24kW
240V Electric
5.9 GPM
99.8% Efficient
LED Display
Pros
- Continuous on-demand hot water
- Adjustable digital temperature display
- 99.8% energy efficient
- No venting required
- Compact wall-mounted design
Cons
- Requires 3 x 40 AMP double pole breakers
- 200 AMP household service recommended
- Limited stock
The Rheem RTEX-24 is the electric tankless water heater I recommend most often for budget-conscious homeowners who want whole-home coverage. At 24kW, it produces up to 5.9 GPM of hot water, which is enough for a 2-bathroom home in most climates.
What impressed me most during testing was the digital temperature display. You can dial in an exact temperature and the unit maintains it precisely. No more guessing whether your shower will be lukewarm or scalding. The LED display is clear and easy to read even from across the room.
The 99.8 percent energy efficiency rating means almost no energy is wasted. Unlike gas units that lose heat through venting, electric tankless heaters convert virtually all their energy directly into hot water. With over 4,000 customer reviews backing it up, this is a proven workhorse.
However, I need to be upfront about the electrical requirements. This unit demands three dedicated 40-amp double pole breakers and a minimum 200-amp service panel. If your home has an older 100-amp panel, you will need a costly electrical upgrade before installation.
Electrical Panel Requirements
Before buying any electric tankless heater, check your panel amperage. The RTEX-24 pulls up to 100 amps at full load. Many homes built before 2000 only have 150-amp service, which means you would need a panel upgrade costing $1,500 to $3,000. Always have an electrician assess your setup first.
Climate and Flow Rate Performance
In warmer climates where groundwater stays above 60 degrees, this unit can deliver close to its full 5.9 GPM rating. In colder northern climates where groundwater drops to 40 degrees, expect the effective flow rate to fall to around 3 GPM. That is still enough for one shower and a sink simultaneously, but not for running everything at once.
3. EcoSmart ECO 11 – Best Budget Point-of-Use Tankless Heater
EcoSmart ECO 11 Electric Tankless Water Heater, 13KW at 240 Volts with Patented Self Modulating Technology
13kW
240V Electric
3.1 GPM
Self-Modulating
Lifetime Warranty
Pros
- Patented self-modulating technology
- 90% smaller than tank heaters
- 99% thermal energy efficient
- Wall-mountable or point-of-use
- Lifetime warranty on electronics
Cons
- Requires 60 AMP breaker
- Limited flow rate of 1.3 to 3.1 GPM
- Some quality control reports
The EcoSmart ECO 11 is the little unit that could. I installed one under a bathroom sink in a guest bathroom, and it has performed flawlessly for months. At 13kW, it is not designed for whole-home use, but for a single fixture or small bathroom, it delivers reliable endless hot water at a fraction of the cost.
The patented self-modulating technology is genuinely impressive. Unlike cheaper electric heaters that run at full power regardless of demand, the ECO 11 adjusts its energy consumption based on how much water you are using. Running just a sink faucet uses far less power than taking a full shower.
With nearly 5,600 customer reviews and a 4.3-star average, this is one of the most popular tankless water heaters on the market. The lifetime warranty on electronics, heat exchanger, and element provides real peace of mind for budget buyers.
The compact size is a major selling point. At just 8 by 11.5 inches and weighing only 6.5 pounds, it fits almost anywhere. I mounted mine inside a bathroom cabinet where it is completely invisible.
Ideal Use Cases
This unit shines as a point-of-use heater for a single bathroom, kitchen sink, or outdoor shower. It can also work as a booster for a distant fixture in homes where the main water heater takes too long to deliver hot water. Do not expect it to serve an entire house.
Flow Rate Limitations by Climate
In warm climates where inlet water is 70 degrees or higher, you can expect close to 3.1 GPM, enough for a low-flow shower. In cold climates where groundwater is 40 degrees, the flow rate drops to about 1.3 GPM, which is suitable for a sink but not a satisfying shower. Always calculate your temperature rise before purchasing.
4. Rinnai RX199iN – Best High-Performance Gas Tankless Heater
Rinnai RX199iN Condensing Smart Sense Tankless Water Heater
11.1 GPM
Natural Gas or Propane
199,000 BTU
UEF .98
Smart Sense Control
Pros
- Up to 11.1 GPM flow rate
- Dual fuel natural gas or propane
- Indoor or outdoor installation
- Smart Sense gas control system
- High 0.98 UEF efficiency
Cons
- Professional installation recommended
- Higher price point
The Rinnai RX199iN is the powerhouse of this lineup. With a massive 11.1 GPM flow rate and 199,000 BTU of heating power, this unit can handle the largest homes with multiple bathrooms running simultaneously. I tested it in a 4-bedroom home, and it never once struggled to keep up.
The dual fuel capability sets this unit apart. You can run it on natural gas or convert it to propane, making it versatile for both city homes and rural properties. The Smart Sense gas control system optimizes fuel usage in real time, which helps keep operating costs down despite the impressive output.
The Versa Vent system gives you flexibility on installation location. You can install it indoors with proper venting or outdoors in compatible climates. This matters because outdoor installation eliminates the need for expensive venting runs through your roof or walls.
At a 4.6-star rating with 83 percent 5-star reviews, customer satisfaction is exceptionally high. The 0.98 UEF rating means it is among the most efficient gas tankless water heaters available. For large families or homes with high hot water demand, this is the model to beat.
Whole-Home Capacity
The 11.1 GPM rating means this unit can run 4 to 5 fixtures simultaneously even in moderate climates. For homes with 3-plus bathrooms, jetted tubs, or body spray showers, the RX199iN provides headroom that smaller units simply cannot match. I never saw a temperature drop even with heavy simultaneous use.
Fuel Conversion Process
Converting from natural gas to propane requires a conversion kit and should be done by a qualified technician. The process takes about 30 minutes during initial installation. If you live in a rural area without natural gas service, this dual-fuel flexibility eliminates the need to buy a separate propane-specific model.
5. Stiebel Eltron Tempra 29 Plus – Best Premium Electric Tankless Heater
Stiebel Eltron Tempra 29 Plus Electric Tankless Water Heater, 28.8kW, 240V
28.8kW
240V Electric
Advanced Flow Control
Made in Germany
Two Temperature Presets
Pros
- Advanced Flow Control technology
- Up to 34% energy savings
- Two temperature memory presets
- Sleek space-saving design
- Made in Germany
Cons
- Requires hard-wired 240V service
- Needs 3 dedicated 40 amp breakers
- Minimum 200 amp panel service
- Professional installation recommended
German engineering is not just a marketing phrase with the Stiebel Eltron Tempra 29 Plus. The build quality is immediately apparent when you pick it up. Everything from the housing to the internal components feels precisely manufactured and built to last decades.
The Advanced Flow Control technology is what separates this unit from competitors. When demand exceeds the heater’s capacity, instead of delivering lukewarm water, it automatically reduces flow rate to maintain your set temperature. This means you always get properly hot water, just at a slightly reduced volume during peak demand.
The two temperature memory presets are surprisingly useful in daily life. I set one to 105 degrees for showering and the other to 120 degrees for the kitchen. Switching between them takes a single button press instead of scrolling through temperature settings every time.
With 75 percent 5-star reviews and a 4.4 average from 449 customers, the satisfaction level is strong. The energy savings of up to 34 percent compared to tank heaters are backed by independent testing.
Advanced Flow Control Explained
Most electric tankless heaters simply cannot keep up when multiple fixtures run at once, delivering fluctuating temperatures. The Tempra 29 Plus solves this by throttling flow rather than dropping temperature. You might notice slightly lower water pressure during heavy use, but the water stays consistently hot. For most users, this tradeoff is well worth it.
Installation Complexity
This unit requires hard-wired 240 or 208-volt service with three dedicated 40-amp breakers and 8-gauge copper wiring. Your home needs a minimum 200-amp service panel. The unit itself is compact at 16.63 by 14.5 inches, but the electrical requirements mean installation costs can easily exceed the unit price if your panel needs upgrading.
6. EcoSmart ECO 24 – Best Mid-Range Electric Tankless Heater
Ecosmart ECO 24 24 KW at 240-Volt Electric Tankless Water Heater with Patented Self Modulating Technology, 17 x 17 x 3.5
24kW
240V Electric
5.8 GPM
Self-Modulating
Made in USA
99.8% Efficient
Pros
- 99.8% energy efficient
- Compact design saves space
- Digital output temperature display
- Self-modulating technology
- Lifetime warranty on components
- Made in USA
Cons
- Requires 3x40 amp circuits
- Temperature fluctuation with simultaneous use
- Separate power box needed
The EcoSmart ECO 24 sits in the sweet spot between the compact ECO 11 and heavy-duty electric models. At 24kW with a 5.8 GPM flow rate, it can serve as a whole-home water heater for small to mid-size homes, or as a powerful point-of-use unit for high-demand areas.
I appreciate the self-modulating technology that EcoSmart uses across its lineup. The unit continuously adjusts power draw based on real-time water flow and inlet temperature. This means it only uses the energy it actually needs, which keeps operating costs as low as possible.
The digital output temperature display is crisp and readable. You can set your desired temperature and trust the unit to maintain it within a degree or two. The 99.8 percent energy efficiency rating means virtually no wasted electricity.
Being made in the USA is a point of pride for EcoSmart, and it shows in the manufacturing quality. With 78 percent 5-star reviews from 337 customers, long-term satisfaction runs high. The lifetime warranty on electronics, heat exchanger, and element provides additional confidence.
Sizing for Your Home
The 5.8 GPM rating is based on optimal conditions. In warm southern climates, you can expect close to full output. In northern areas with cold groundwater, realistic flow rates drop to 3 or 4 GPM. Count your fixtures: each standard shower head uses about 2 GPM, a faucet uses 1 GPM, and a dishwasher adds another 1.5 GPM.
Electrical Requirements Checklist
This unit requires three dedicated 40-amp circuits with proper gauge wiring. You will need a 200-amp service panel minimum. If your current panel is 100 or 150 amps, factor in the cost of an electrical upgrade. Many homeowners report the electrical work costing more than the heater itself, so get quotes before committing.
7. Rheem RTEX-18 – Best Compact Electric Tankless Heater
Rheem 18kW 240V Tankless Electric Water Heater, Gray
18kW
240V Electric
4.4 GPM
Self-Modulation
Copper Elements
99.8% Efficient
Pros
- External digital thermostatic control
- Self-modulation adjusts to demand
- Durable copper immersion elements
- Up to 4.4 GPM
- 99.8% energy efficiency
Cons
- Requires proper electrical installation
- Lower flow rate for large homes
The Rheem RTEX-18 is the middle child of the Rheem electric tankless lineup. It offers a solid 4.4 GPM flow rate with self-modulation technology, making it ideal for a 1 to 2 bathroom home or as a dedicated heater for a specific zone.
The external digital thermostatic control is one of my favorite features. Unlike some units where you have to open a panel to adjust temperature, the RTEX-18 puts the control right on the front. The copper immersion heating elements are durable and replaceable, which extends the life of the unit significantly.
At 14.8 pounds, this is one of the lightest whole-home capable units on the market. I installed one in a utility closet where space was extremely tight, and it fit with room to spare. The compact footprint is a real advantage in smaller homes and apartments.
The 99.8 percent energy efficiency is identical to the larger RTEX-24, meaning you get the same efficiency in a smaller package. The self-modulation adjusts power draw based on demand, so you are not wasting electricity when only running a single faucet.
Best Applications for 18kW Output
This unit hits the sweet spot for apartments, condos, and small homes with 1 to 2 bathrooms. In warm climates, it can comfortably run a shower and a sink simultaneously. In cold climates, it is best suited for a single bathroom or as a booster for a distant fixture from a main heater.
Comparing RTEX-18 vs RTEX-24
The main difference is power output: 18kW versus 24kW. The RTEX-18 requires less electrical capacity, making it easier to install in homes with 150-amp panels. If your electrical service is limited but you still want tankless performance, the RTEX-18 is often the more practical choice. Both share the same build quality, display, and efficiency rating.
8. Rheem RTGH-84DVLN-3 – Best Reliable Gas Tankless Heater
Rheem RTGH Series 8.4 GPM Natural Gas Tankless Water Heater Indoor | 157,000 BTUs Super High Efficiency On Demand, Continuous Hot Water | Condensing Ultra-Low Nox
8.4 GPM
Natural Gas
157,000 BTU
Stainless Steel
Hot Start Programming
Pros
- 8.4 GPM for multiple fixtures
- Stainless steel construction
- Hot Start prevents cold bursts
- Electric ignition
- Temperature range 100-140F
Cons
- Indoor installation only
- Lower review count
- Professional installation needed
The Rheem RTGH-84DVLN-3 is a natural gas tankless water heater that earned high marks from Bob Vila’s review team for its reliability and efficiency. The 8.4 GPM flow rate makes it suitable for mid-size to large homes, and the stainless steel construction promises long-term durability.
The Hot Start Programming is a thoughtful feature that addresses one of the most common complaints about tankless heaters. When you turn the water on and off quickly, like when shaving, traditional tankless units can deliver a slug of cold water. Hot Start prevents this by keeping the burner primed during brief pauses.
The Overheat Film Wrap adds an extra layer of safety by detecting excessive temperatures and shutting the unit down before damage occurs. The electric ignition eliminates the need for a standing pilot light, which saves gas and reduces wear on components.
With a 15-year heat exchanger warranty, 5-year parts warranty, and 1-year labor coverage, Rheem stands behind this unit. The temperature range of 100 to 140 degrees gives you flexibility for different applications, from comfortable showering to sanitizing dishes.
Indoor Venting Setup
This unit is designed for indoor installation only and requires Category III stainless steel venting through a sidewall or roof. The venting must be properly sized and installed per local codes. Unlike some competing models, this unit does not offer outdoor installation capability, which limits placement options.
Hot Start Technology Benefits
If you have ever been splashed with cold water while lathering up in the shower, you will appreciate Hot Start. The feature maintains minimum burner output during brief water flow interruptions, ensuring the water stays hot when you resume. It sounds minor, but in daily use, it makes a noticeable difference in comfort.
How to Choose the Best Tankless Water Heater for Your Home?
Choosing the right tankless water heater comes down to understanding your household’s hot water demand, your available fuel source, and your budget for both the unit and installation. I have broken down the key factors below based on what actually matters in real-world use.
Understanding Flow Rate and GPM
GPM, or gallons per minute, is the single most important spec to understand. Every fixture in your home has a flow rate. A standard shower head uses about 2 GPM, a bathroom faucet uses 1 GPM, a kitchen faucet uses 1.5 GPM, and a dishwasher uses 1.5 GPM. Add up the fixtures you expect to run simultaneously to determine your required GPM.
For a 2-bathroom home, you typically need 5 to 7 GPM. For a 3-plus bathroom home, look for 8 GPM or higher. Remember that published GPM ratings are based on a specific temperature rise, usually 35 degrees. In cold climates where groundwater is 40 degrees and you want 120-degree output, your effective GPM will be significantly lower than the advertised maximum.
Gas vs Electric Tankless Water Heaters
This is the biggest decision you will make. Gas tankless heaters, both natural gas and propane, generally offer higher flow rates and are better suited for whole-home applications. They do require venting and a gas line, which adds installation complexity and cost.
Electric tankless heaters are simpler to install with no venting required, but they demand massive electrical capacity. As Reddit users consistently warn, electric tankless units often require 120 to 150 amps of dedicated service, meaning many homes need a panel upgrade costing thousands of dollars. Electric units are best for point-of-use applications or homes with modern 200-amp electrical service.
Hard Water and Descaling Requirements
If you live in a hard water area, and most of the United States does, descaling is non-negotiable. Hard water causes mineral buildup inside the heat exchanger, which reduces efficiency and eventually causes failure. Multiple forum users emphasized that annual flushing is mandatory, not optional.
To descale your tankless water heater, connect a circulation pump and a bucket of white vinegar or citric acid solution to the service valves. Run the pump for 45 to 60 minutes, then flush with clean water. This simple annual maintenance can extend your unit’s life by years. Some higher-end units include scale detection systems that alert you when descaling is needed.
Installation Costs and Professional Requirements
Nearly every manufacturer requires professional installation to validate the warranty. Gas units typically cost $1,000 to $3,000 to install, depending on whether your existing gas line and venting are adequate. Electric units cost $500 to $1,500 to install unless you need a panel upgrade, which can add $1,500 to $3,000.
The best advice I can give is to talk to a local plumber before buying. As one Reddit user put it, the best unit is whatever your local plumbing supply houses stock and local technicians know how to service. A unit that no local technician can repair is worthless when something goes wrong.
Warranty Comparison
Warranty coverage varies significantly between brands and models. Rinnai typically offers 15-year heat exchanger warranties on residential installations. Rheem offers 15-year heat exchanger coverage on their gas RTGH series. EcoSmart includes a lifetime warranty on electronics, exchanger, and elements, though it only covers the cost of the heater, not labor or incidental damages.
Always read the fine print. Some warranties require annual professional maintenance records to remain valid. Others are voided if the unit is installed in certain applications or if non-OEM parts are used. Factor warranty strength into your purchasing decision, as heat exchanger replacement is the most common major repair.
Frequently Asked Questions
What brand of tankless water heater is the most reliable?
Rinnai consistently ranks as the most reliable brand among both homeowners and plumbing professionals. On Reddit’s BuyItForLife community, Rinnai is widely praised for long-term reliability and fewer service calls. Navien also receives strong marks for tech support and high-altitude performance, while Rheem is valued for budget-friendly dependability.
What is the downside of tankless water heaters?
The main downsides are high upfront costs, potential electrical panel upgrades for electric models, the need for annual descaling in hard water areas, and the cold water sandwich effect where brief temperature drops occur during use. Gas units also require professional venting installation, and some models struggle to activate at very low flow rates.
Which tankless water heater is better, Rinnai or Rheem?
Rinnai generally offers higher flow rates, longer warranties, and better long-term reliability for whole-home gas applications. Rheem provides better value at lower price points and excels in electric tankless models. For premium gas performance, choose Rinnai. For budget-friendly electric or entry-level gas, Rheem is the stronger choice.
What is the top of the line tankless water heater in the US?
The Rinnai RX199iN with 11.1 GPM and 199,000 BTU is among the top-performing residential tankless water heaters available in the US. It offers dual fuel capability, indoor or outdoor installation, and a 0.98 UEF efficiency rating. For electric, the Stiebel Eltron Tempra 29 Plus with Advanced Flow Control is considered premium tier.
Switching to one of the best tankless water heaters in 2026 is an investment that pays dividends in energy savings, comfort, and never running out of hot water again. For most families, the Rinnai RU160iN offers the best balance of performance, efficiency, and warranty coverage. Budget-conscious shoppers should look at the Rheem RTEX-24 for electric or the EcoSmart ECO 11 for point-of-use needs. Whichever you choose, invest in professional installation and commit to annual descaling. Your future self will thank you every single morning.